Various techniques have been devised in an attempt to maximize the benefit of a trailer. Trailers are, of course, widely used to transport goods, and in particular heavy equipment. U.S. Pat. No. 6,371,505 discloses a double gooseneck trailer for hauling large, heavy loads. U.S. Pa. No. 6,767,172 discloses a low loader trailer, and in particular a front loading flatbed trailer.
Unique problems are presented when transporting a drilling rig, and in particular a drilling rig of a type which includes a coil tubing injector for injecting coil tubing into the well, and a top drive unit for handling conventional threaded tubulars during other well operations. U.S. Publication 2005/0194189 discloses a mobile drilling rig which is fabricated in three sections for transport to and installation at a drilling site. Publication 2004/0240973 discloses a transportable oil rig which includes in one embodiment a mast dolly positioned near the rear of the trailer. The mast dolly includes a set of wheels and an adjustable height support framework to stabilize the dolly and keep it level. The assembly may be made up and disassembled at the well site. Publication 2005/0193645 discloses another mobile drilling rig comprising two substructure sections and a mast section which may be assembled at the well site. Publication 2004/0211598 discloses a drilling rig with a specialized positioning dolly and an adjustable fifth-wheel truck connection for transporting the mast to the drill site for assembly.
The disadvantages of the prior art are overcome by the present invention, an improved mobile drilling rig is hereinafter disclosed.